title: Smad2-dependent downregulation of miR-30 is required for TGF-β-induced apoptosis in podocytes.
abstract: Transforming growth factors beta (TGF-β) are multi-functional cytokines capable of inducing apoptosis in epithelial cells, including glomerular podocytes. We and others have previously shown that podocyte-selective genetic deletion of the microRNA (miR)-processing enzyme, Dicer, caused glomerulosclerosis that was associated with podocyte apoptosis, and the miR-30 family was implicated in the process. Here, we report that apoptosis-associated genes were highly enriched among the predicted targets of miR-30 when compared with randomly selected miRs (26% vs. 4.5 ± 2.1%) or with the known TGF-β-regulated miR-192 (6%), miR-216a (5.1%), and miR-217 (0%). miR-30 family members were abundantly expressed in podocytes in normal mice but were downregulated in albumin/TGF-β transgenic mice with podocyte apoptosis and glomerulosclerosis. In vitro, TGF-β downregulated miR-30s in wildtype and Smad3-deficient, but not Smad2- or Smad2/Smad3-deficient, podocytes. The TGF-β-induced activation of caspase 3 and an increase in TUNEL-positive nuclei were significantly inhibited by the lentivirus-mediated overexpression of miR-30d, but not by a scrambled control miR, in podocytes. TGF-β stimulated the phosphorylation of pro-apoptotic p53 in podocytes with lentiviral expression of a scrambled miR, but not in podocytes expressing miR-30d. In contrast, miR-30d had no effect on the phosphorylation of pro-apoptotic p38 MAP kinase induced by TGF-β. Thus, we report that Smad2-dependent inhibition of miR-30s in podocytes is required for the activation of p53 and the induction of apoptosis by TGF-β. These results demonstrate a novel functional role for miR-30 in podocyte survival and indicate that the loss of miR-30 survival signaling is a novel and specific mechanism of TGF-β-induced podocyte apoptosis during glomerulosclerosis. We propose the therapeutic replacement of miR-30 as a novel strategy to prevent the podocyte apoptosis that is characteristic of progressive glomerular diseases.
authors.affiliation: Department of Medicine, Mount Sinai School of Medicine, New York, New York, United States of America.
authors.forename: Shaolin
authors.initials: S
authors.lastname: Shi
authors.forename: Liping
authors.initials: L
authors.lastname: Yu
authors.forename: Taoran
authors.initials: T
authors.lastname: Zhang
authors.forename: Haiying
authors.initials: H
authors.lastname: Qi
authors.forename: Sandhya
authors.initials: S
authors.lastname: Xavier
authors.forename: Wenjun
authors.initials: W
authors.lastname: Ju
authors.forename: Erwin
authors.initials: E
authors.lastname: Bottinger
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000235:genetics*; D053148:Caspase 3 / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D015536:Down-Regulation / Q000235:genetics*; D006801:Humans; D020287:In Situ Nick-End Labeling; D051379:Mice; D008822:Mice, Transgenic; D035683:MicroRNAs / Q000235:genetics* / Q000378:metabolism*; D050199:Podocytes / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics; D051899:Smad2 Protein / Q000235:genetics* / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000235:genetics* / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism
chemical_list: D035683:MicroRNAs; C534715:Mirn30d microRNA, mouse; D051899:Smad2 Protein; C497783:Smad2 protein, mouse; D016212:Transforming Growth Factor beta; D016159:Tumor Suppressor Protein p53; D048051:p38 Mitogen-Activated Protein Kinases; D053148:Caspase 3